This invention relates generally to an arrangement for preventing the pollution of a body of water having variable levels and more particularly to a buoy type oil gate which holds back pollutant products. Previously, oil spills into a stream of water having variable flow and, therefore, variable water levels, involved the use of high priced oil separators through which the flow of water was made to pass. In addition to expensive equipment costs required for an oil separator system, a requirement exists for much costly manpower and maintenance for effective operation. The high costs have inhibited adoption of ecological control systems because of the economic impact of high cost maintenance and equipment on the industries causing the pollution. My invention avoids the high costs attendant to prior art water pollutant control systems.